I logged in initially with my Facebook account in Stackoverflow. Then I created several accounts in StackExchange sites. Today I was casually visiting data.SE and wanted to login. but there was no arrangement to use Facebook credential. so I used rather my Google account to login and to my surprise I found I have logged in as John.doe10225. My avatar is still the same. But in other sites when I logged in it came as Mistu4u. This is the first time I got different result.